Process for producing sulphonium compounds

ABSTRACT

Dialkyl-methyl sulfonium chlorides, having at least one alkyl group of at least four carbon atoms are produced by the reaction of a higher dialkyl sulfide with methyl chloride at 60*-100*C in the presence of specified quantities of hydrofluoric or hydrochloric acid.

United States Patent 1 1 Campen et al.

[ Sept. 11, 1973 PROCESS FOR PRODUCING SULPHONIUM COMPOUNDS [75] Inventors: Jan P. Campen; Ernest L. T. M.

Spitzer; Wilhelmus A. A. Senden; Jeffrey S. Hill, all of Amsterdam, Netherlands [73] Assignee: Shell Oil Company, New York, N.Yv

[22] Filed: Aug. 18, 1971 [21] Appl. No.1 172,908

[30] Foreign Application Priority Data Aug. 26, 1970 Great Britain 4l,067/70 [52] U.S. Cl 260/607 B, 260/607 B [51] Int. Cl C07C 149/46 [58] Field of Search 260/607 B [56] References Cited UNlTED STATES PATENTS 2,252.08] 8/l94l Lieber 260/607 B Primary Examiner-Lewis Gotts Assistant ExaminerD. R. Phillips Attorney-Howard W. Haworth et al.

p [57] ABSTRACT 6 Claims, N0 Drawings PROCESS FOR PRODUCING SULPI-IONIUM COMPOUNDS BACKGROUND OF THE INVENTION AND PRIOR ART This invention relates to the preparation of higher dialkyl-methyl sulfonium chlorides. As used herein, higher dialkyl-methyl sulfonium chloride refers to a sulfonium chloride having at least one alkyl group containing a chain of at least four carbon atoms.

Spitzer et al., U.S. Pat. No. 3,432,257 (issued Mar. 11, 1969) disclose the use of higher dialkyl sulfonium chlorides as extracting agents in the winning of metal values from aqueous solutions. The method taught by Spitzer et al for preparing dialkyl sulfonium chlorides contemplates two steps:

1. methylation of a dialkyl sulfide with dimethyl sul fate, and

2. conversion of the resulting sulfonium methyl sulfate to the corresponding chloride by an exchange reaction with hydrochloric acid. This two-step procedure is in accordance with prior art methods, for example, I-Iouben-Weyl, Methoden der Organischen Chemie, Volume 9, pages 175-194. This two-step reaction sequence suffers from a number of practical disadvantages. First, dimethyl sulfate is a toxic and expensive reactant. Secondly,.the dimethyl sulfate participates in the reaction with only one of its two methyl groups. Finally, the exchange reaction with hydrochloric acid proceeds slowly and requires many successive steps for completion. It would be desirable if the above-indicated reaction steps could be combined into a single step, and employ an alkyl chloride as an alkylating agent.

Lieber, U.S. Pat. No. 2,252,081 (issued Aug. 12, 1941) teaches that sulfonium chlorides may be prepared at or slightly below room temperature by the reaction of an organic sulfide with an alkyl chloride in an inert, anhydrous alcohol. Britton et al., U.S. Pat. No. 2,366,176 and U.S. Pat. No. 2,402,016 (issued Jan. 2, 1945 and June 11, 1946, respectively) broadly suggest a spontaneous addition reaction" for preparing sulfonium halides from alkyl halides and dialkyl sulfides containing as many as eighteen carbon atoms in the alkyl moieties. Funazukuri, Japanese Patent Application 196l-2,l73 (filed Oct. 11, 1957; Chemical Abstracts, 56 8566cc (1962)) teaches the preparation of trimethyland triethylsulfonium halides by the reaction of dimethyland diethyl-sulfides with in situ generated, corresponding alkyl halides.

As shown in the comparative examples which follow below, the foregoing one-step procedures for preparing low molecular weight sulfonium chlorides may not be extended to methyl-homologs of higher molecular weight.

BRIEF DESCRIPTION OF THE INVENTION It has now been found that dialkyl-methyl sulfonium chlorides having at least one alkyl group of at least four carbon atoms may be prepared in excellent yield by the reaction of a higher dialkyl sulfide with methyl chloride at about 60 to about 100C in the presence of at least 1.5 molecular equivalents of a hydrohalic acid catalyst per mole of dialkyl sulfide, wherein the hydrohalic acid catalyst is selected from the group consisting of hydrochlorie and hydrofluoric acids.

DETAILED DESCRIPTION OF THE INVENTION A. The Dialkyl Sulfide Reactant.

The higher dialkyl sulfide reactant possesses at least one alkyl moiety containing a chain of at least four carbon atoms. Although the total number of carbon atoms in the dialkyl sulfide may vary between rather wide limits, the preferred dialkyl sulfides have an effective chain length" of at least nine atoms. Particularly preferred dialkyl sulfide substrates are those having effective chain lengths of between about 15 and about 25 atoms. By effective chain length" is meant the number of atoms, other than hydrogen, which collectively form the longest chain present in the molecule. Such a chain may contain not only atoms of carbon but, in addition, a sulfur atom. Thus, the effective chain length of, for example, a didodecyl sulfide amounts to 25 atoms, since the longest chain consists of (2 X 12) 24 carbon atoms plus one sulfur atom. Examples of suitable dialkyl sulfides are methylheptyl sulfide, diisoamyl sulfide, dicetyl sulfide, and the like. Preferred sulfide substrates are those having from about eight to about 12 carbon atoms, inclusive, per alkyl moiety. Additionally preferred are those alkyl groups present in the dialkyl sulfide which are secondary alkyl in structure.

B. The Acid Catalysts.

The catalytic activity of hydrofluoric and hydrochloric acids is surprising in view of the known tendency of acids to induce disproportionation ractions in higher sulfides (see Houben-Weyle, supra, at page 183). Such disproportionation activity would be expected, in the process of the present invention, to result in a reduced yield of the desired sulfonium compound. The use of hydrofluoric and hydrochloric acids as catalysts in the preparation of higher dialkyLmethyl sulfonium chlorides offers at least two major benefits. First, with proper precautions, the acid catalysts are safe and economical to work with. Secondly, because of their volatility, hydrofluoric and hydrochloric acids are easily removed from the reaction product, thus minimizing purification problems. The terms hydrofluoric acid and hydrochloric acid are used to broadly indicate the respective hydrogen halides, independent of the presence or absence of water.

C. Reaction Conditions The reaction may be carried out with or without the addition of a solvent. When a solvent is employed, inert materials such as methanol, diisopropyl ether, dichloroethane or toluene are preferred. Generally, however, it is preferable to effect the alkylation in the absence of a solvent. In view of the volatile nature of reactants and acid catalysts which participate in the reaction, it is generally advantageous to maintain them substantially in a liquid state. Pressures in the range of about 5 to about 100 atmospheresgauge will generally suffice, depending in part upon the type and amount of substrates and acid catalysts which are present. Desirably, a high ratio of liquid to gas is maintained within the reaction vessel, preferably at least 1:1, so that the reactor contains a maximum proportion of liquid. The reaction is typically conducted at a temperature between about 60 and about 100C; preferably, the temperature is maintained between about and about C. The

time of reaction is not critical in the formation of the desired dialkyl sulfonium chlorides, and may vary, for instance, between about 2 and about 12 hours.

Water is preferably excluded from the reaction mixture, although the addition of small amounts, i.e., up to about 5 percent by weight based on the total reactants, is not detrimental. The ratio of reactants, one to anreacted methyl chloride and hydrohalic acid catalyst, were allowed to escape. After further cooling to room temperature, the two-phase product was separated into a sulfonium chloride and a residual disulfide layer. Furother, and to the hydrohalic acid catalyst, is variable. 5 ther experimental details appear in Table 1.

TABLE 1.-1REPARATION OF METHYL DI-SEC. OCTYL SULFUNIUM CHLO RID E Molar Yield of ratio, sulfonium sulfide: chloride, CI'IIiCl percent hydrohalie Rene based on acid Temp., Pressure, time, disuliidc Catalyst catalyst C. atg. hours charged 1:1. 2:4 80 6 2 50 1:1. 2:4 80 4 61 1 :2:4 80 12)10 4 75 123:4 80 12 10 4 82 114:4 80 14-)10 4 88 1:2:4 70 8 4 58 1:2:4 90 13- 9 4 82 1:2:1 80 12-- 11 4 23 1:2:4 9O 17 13 6 90 1:4:4 80 40- 2fi 4 68 1:424 80 46 28 8 90 1 :4210 80 57 50 4 90 1:1.214 80 51-- 25 8 72 1:].221 80 Z-- 16 ii 16 122:4 8U 28- 21 4 39 1 Instead of di octy s11 flde, di-sec decylsullide was used.

The molar ratio of methyl chloride to dialkyl sulfide in the reacting mixture is at least 1:1, and preferably is within the range of from about 1.521 to about 6:1. The formation of sulfonium chlorides proceeds in a particularly effcient manner when the molar ratio of methyl chloride to dialkyl sulfide is in the range of from about 3:1 to about :1. At least 1.5 molecular equivalents of the hydrohalic acid catalyst are present per mole of dialkyl sulfide in the reacting mixture, and preferably at least three but no more than about molecular equivalents are so employed.

The sulfonium chloride product may be recovered by known techniques, for example, by flashing off volatile components (hydrofluoric acid, hydrochloric acid, methyl chloride, and the like), water washing, distillation, and by similar procedures. Where hydrofluoric acid has been employed as the acid catalyst, some fluoride may remain in the sulfonium chloride; this may be removed by a wash with concentrated calcium chloride, which precipitates calcium fluoride.

An advantageous method of recovering volatile methyl chloride and/or hydrohalic acid catalyst is to condense the pressurized gases in a pressure vessel cooled to a temperature of about 100 to about 30C. By such a technique, the size of compression equipment required for the highly corrosive recycle streams may be minimized.

ILLUSTRATIVE EMBODIMENTS 1. Preparation of Di-sec.0ctylmethyl Sulfonium Chloride Di-sec.octyl sulfide was reacted in an autoclave with methyl chloride in the presence of hydrochloric or hydrofluoric acid catalysts. The sulfide was weighed into a polypropylene beaker containing a magnetic stirring bar. The beaker was placed into an autoclave which was subsequentlycooled to 30C. Cold methyl chloride and hydrohalic acid catalyst were then added, and the autoclave was sealed and heated to reaction temperature. After completion of the reaction the autoclave was cooled to 50C and the gases, comprising un- 11. Preparation of Di-Sec.Decylmethyl Sulfonium Chloride.

A crude sulfide mixture (168 g) containing 67.1%w of di-sec.decyl sulfide was added to a 500 m1 l-lastelloy C stirred autoclave. The autoclave was cooled to 30C, whereupon 81 g of methyl chloride and 130 g of HCl were added. After sealing, the autoclave temperature was brought to 80C, corresponding to a pressure of atm. After 4 hours of reaction at C, the autoclave was connected to a similar autoclave, evacuated, and maintained at a temperature of 53C to remove gaseous components of the reaction mixture. By this technique, 91 percent of the unreacted methyl chloride and 77 percent of the HCl condensed in the cold autoclave after pressure equilibrium had been achieved. These materials were employed in a subsequent batch. After cooling to room temperature, the reactor autoclave was brought to atmospheric pressure. The crude reaction product contained di-sec.decylmethylsulfonium chloride (88 percent yeild) and 2.6 mole HCl/mole of reaction product. The crude product was extracted five times with 25 m1 of pentane to remove unconverted organic material (sulfide, polysulfide, mercaptan and sec-decylchloride), and subsequently stripped for 30 minutes at 20C and 15 mm Hg. The extracted and stripped sulfonium chloride, containing 1.5 mole HCl/mole sulfonium chloride to enhance its stability, was obtained in a yield of 86 percent, basis dialkylsulfide charge.

COMPARATIVE EXAMPLE In a series of runs, attempts were made to extend the teachings of Lieber, U.S. Pat. No. 2,252,081, and Funazukuri, Japanese Patent Application l96l2,l73 (Chemical Abstracts, 52: 8566cc (1962)), to the preparation of higherdialkyl-methyl sulfonium chlorides. These runs also were directed to evaluating the spontaneous addition reaction of a dialkyl sulfide with an alkyl halide, wherein the alkyl moieties contain from one to 18 carbon atoms, as taught by Britton et al, U.S. Pat. No. 2,366,176 and U.S. Pat. No. 2,402,016. As

2. The process of claim 1 wherein the higher dialkyl sulfide has an effective chain length of at least nine atoms.

3. The process of claim 2 wherein the alkyl moieties of the higher dialkyl sulfide independently contain TABLE 2.ATTEM1TED EXTRAPOLATION OF U.b. 2,252,081ANI) JAPANESE PATENT AllLl- CATION 19612,173 TO HIGHER DIALKYL SULFIDES Dialkyl sull'onium chloride Molar yield,

Ratio, Reacpercent m.

CHsClt Temper- Prestion on dialkyl Dialkyl ature, sure, time, sulfide Dialkyl sulfide sulfide Soovent 1 atm. hrs. charge Run:

A ])i|m-.Lliyl sulfide .s 1.2 80 9-14 2 40 1 1)1-|l-pr0pyl sulli 1.2 80 21-14 2 15 L 1 do 120 9-12 1 0. 5

M 1 1,2-dieh1 oethane 120 9-12 1 0. 5

1 60 grams of solvent were employed per mole of dialkyl sulfide.

2 In this run, 10% m. hydrochloric acid, basis dialkyl sulfide, was added to the reaction mixture.

from about eight to about 12 carbon atoms per moiety. 4. The process of claim 3 wherein the alkyl moieties are secondary alkyl.

5. The process of claim 1 wherein the molar ratio of methyl chloride to higher dialkyl sulfide is at least lzl. 6. The process of claim 5 wherein the molar ratio of methyl chloride to higher dialkyl sulfide is maintained within the range of from about 1.521 to about 6:1.

* t k l 

2. The process of claim 1 wherein the higher dialkyl sulfide has an effective chain length of at least nine atoms.
 3. The process of claim 2 wherein the alkyl moieties of the higher dialkyl sulfide independently contain from about eight to about 12 carbon atoms per moiety.
 4. The process of claim 3 wherein the alkyl moieties are secondary alkyl.
 5. The process of claim 1 wherein the molar ratio of methyl chloride to higher dialkyl sulfide is at least 1:1.
 6. The process of claim 5 wherein the molar ratio of methyl chloride to higher dialkyl sulfide is maintained within the range of from about 1.5:1 to about 6:1. 